A compactor (sometimes referred to as a vibrating roller) is, in general, a machine used to compact a material (e.g., soil, a base layer, an anti-frost layer, asphalt, and/or the like) over which the compactor moves. A compactor can include a vibratory system that causes a vibration component of the compactor to vibrate as the compactor moves over the material, thereby improving compaction of the material (e.g., as compared compaction without vibration). For example, the vibratory system may include an output motor (e.g., a hydraulic motor) that is connected, via an output shaft, to an unbalance vibrator arranged in a drum of the compactor. Here, the output motor provides output torque to the output shaft. The output torque causes the unbalance vibrator to rotate, which, due to the unbalanced nature of the unbalance vibrator, causes the drum to vibrate. Generally, the output motor is driven by an input pump (e.g., a hydraulic pump) that is connected, via an input shaft, to an engine of the compactor (e.g., an internal combustion engine), that provides input torque to the input pump. The compactor also typically includes a (separate) propulsion system, including a propulsion motor, associated with moving the compactor over the material.
In operation, the vibratory system and the propulsion system can be started at the same time (e.g., such that the drum begins vibrating when the compactor begins moving), which requires a comparatively high amount of engine power requirement. However, once the vibratory system is started, the vibratory system requires comparatively less engine power in order to maintain a given vibratory speed. As such, the amount of engine power required after startup of the vibratory system is comparatively lower than the amount of engine power required at startup. Nonetheless, the compactor engine must be designed to provide the amount of engine power required when the vibratory system and the propulsion system are started at the same time.
One attempt to providing startup assistance to a vibratory system, in order to reduce required engine power, is disclosed in U.S. Pat. No. 9,782,800 that issued to Robert Bosch GmbH on Oct. 10, 2017, (“the '800 patent”). In particular, the '800 patent discloses an energy recovery possibility for a vibrating roller by means of a vibratory drive. The basic idea disclosed in the '800 patent is to use a vibratory drive of a vibrating roller for energy recovery, where the vibrating roller comprises an unbalance vibrator that is inserted in a rotatable fashion in a drum that is driven by a propulsion motor. In the '800 patent, the unbalance vibrator is mechanically coupled to a hydraulic motor (via an output shaft), and the hydraulic motor is supplied with a pressure medium by a hydraulic pump. According to the '800 patent, the vibratory drive includes a high-pressure accumulator that serves to accommodate pressure medium delivered by the hydraulic motor in an “overrun mode” (i.e., when a torque is applied from the output shaft to the hydraulic motor in a coasting mode of the unbalance vibrator). In other words, the '800 patent discloses the vibratory drive as a drive which is relevant for the recovery of energy.
According to the '800 patent, in one embodiment, the hydraulic pump and the hydraulic motor are arranged in a closed circuit in which, in the overrun mode, a downstream connection of the hydraulic motor can be fluidically connected to the high-pressure accumulator, and in an acceleration mode (starting up of the unbalance vibrator) an upstream connection of the hydraulic motor can be fluidically connected to the high pressure accumulator. As an alternative embodiment, the '800 patent describes that the hydraulic pump and the hydraulic motor are arranged in an open circuit in which the downstream connection of the hydraulic motor can be fluidically connected to a tank or to the high-pressure accumulator.
While the vibratory drive of the '800 patent may provide some plausible solutions for energy recovery using a vibratory drive, the vibratory drive of the '800 patent has numerous shortcomings. For example, the vibratory drive of the '800 patent discloses vibratory drives that add power (from the high-pressure accumulator) at the hydraulic motor. In operation, such a configuration requires tight coordination between the hydraulic pump and the hydraulic motor of the vibratory drive, which can result in complex switching scenarios, timing issues, and/or the like. Furthermore, the vibratory drive disclosed in the '800 patent provides a high-pressure accumulator that accommodates pressure medium only in the overrun mode, but not during other times of operation, such as during “normal” operation of the vibrating roller.
The vibratory system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.